The result indicated eight potential risk factors of categorical variables, including tumor stage, tumor location, alcohol drinking history, DM, heart disease, pre-operative chemotherapy, operative surgeon, and re-open (Table 1), as well as 14 potential risk factors of continuous variables, including BMI, RBC, WBC, Hb, Hct, percentage of neutrophil, albumin, glucose, Cr, Na, flap length, operative time, and the units of transfused packed RBC or plasma (Table 2). Here, GSTM1 is linked to diabetes mellitus.